Update dead dining philosophers link to the 1.4.0 book example.

README.md

@@ -118,7 +118,7 @@ Check out the [Iterators chapter of the book](https://doc.rust-lang.org/stable/b
 
 ### Threads
 
-See [the Dining Philosophers example](https://doc.rust-lang.org/stable/book/dining-philosophers.html) and the [Concurrency Chapter](https://doc.rust-lang.org/stable/book/concurrency.html) from the book.
+See [the Dining Philosophers example](https://doc.rust-lang.org/1.4.0/book/dining-philosophers.html) and the [Concurrency Chapter](https://doc.rust-lang.org/stable/book/concurrency.html) from the book.
 
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